How about removing the stereo pops from mono records?

Hi all.

It seems to me that it should be possible to remove a significant amount of noise from mono records by digitizing them in stereo and removing everything that’s not common to both channels. A lot (most?) of the noise is in stereo, being damage to one groove wall or the other but often not both.

Is anyone doing this? It’s easy to get the difference information, but I worked on removing the stereo information quite a while in Sound Forge and never seemed to come up with a method that worked well.

If I remember right, I took the difference (L - R) info, made the original recording mono, then tried to subtract the difference info from it by inverting its phase and mixing it. No good. Hm, then I remember something about trying the mid/side recording conversion, and that must not have worked well either.

Any ideas welcome. Thanks!

You want what is common to both L and R and reject everything else ? : that’s “centre pan isolation”, a.k.a. “centre pan extraction”.

The result of the inversion trick is what is not common to both channels: i.e. “centre pan removal”, (the opposite of what you want).

There is a free plugin which works with Audacity 1.3.11 which will do centre pan isolation it’s called Kn0ck0ut.

Similar plugins and standalone software which does this are available, (NB the results are not perfect: usually lots of digital artifacts).

Of course when centre pan isolation is applied to a stereo track the result is mono.

Thanks a lot for that info.

This explains why centre pan isolation can’t be done by inversions …

Before I even look at that…

I realized at some point that the inversion wouldn’t work, because the initial L-R step already involved inverting one of the channels. So there was no way to do another subtraction from the original signal using the result of that first subtraction.

Thanks for the link.